Process for selective hydrogenation of petroleum stocks



isimultaneously in accordancexwith :this. :invention. also a feature of.this invention that. there is. nomemoval t a-snam PROCESS FOR SELECTIVETHYDROGENATION OF PETROLEUM, STDCKS Harvey, Hennig Crystal Lake,Jll.,,;assignor1to The Pure Oil Company, ;Chicago, 111., acorporation.of Ohio H Application September 13, 1955; Serial No. 533,978

.SCIaimS; (Cl..208-.-,-1144) The present inventionrelates toa processforhydro- .of dilferent properties are simultaneously treatedinonehydrogenation unit under difierent processing conditions.

The basic idea of this invention is that several) dissimilar petroleumstocks are hydrogenated in an integrated series Patented Mar. 17, I959ice 2 Briefly, oneembodiment of the process. comprisessubjecting, f3.refractory stock such as ,coker gas-oil, heavy catalytic,, cycle-oil, ora heavy gas-oil high in sulfur compounds, separately or simultaneously,to hydrogenation in a-first cat aly stic zone under conditions todesulfurize, saturate olefinic and diolefinic linkages, and, if desired,partially-hydrogenate some aromatic compounds. Coker gas-oilmaybeobtained from such processes as delayed coking, thermaldecarbonization, continuous contact cok ing,- or fluid coking. Heavycatalytic cycle oil is a productofthe oatalystic cracking of hydrocarbonoils. Heavygas-oil containing 0.2 to 2.0% or more by weight of sulfurcompounds tmay be produced by fractionation of crude genating petroleumstocks whereby ainumbcr of-stocks of reaction-zones under differentprocessing-conditions such as temperature, pressure,time ofcontactandhydrogenpartial pressure. A,,further'particular advantage ofithe'invention is that the'reactor conditions can be controlledby theconditions applied'to the various feeds, rather than by a recyclingprocess-wherein excess-hydro gen is sent back to the reactors fortemperaturegcontrol as in presentpractice. This invention is carried outby providinga series of several catalyst zonesor catalyst beds in onereactor 'or-in a series of reactors into which various petroleum. Theproducts from this first reaction zone pass into asecond zone to meetand mix with a second feed stock which is less refractory than the firstfeed stock. I The second feed =stock maybe alight catalytic cycle-oil,"heavy thermal or cokeranaphtha, or a highsulphu'r distillate, such asdieselfuel'stock, burning oil, stove oil, or kerosene. The catalyticcycle-oii is produced by: catalytic cracking of hydrocarbon oils.-Heavy-thermal or coker naphtha is genenallyproduced-by the cokingprocesses .alreadyreferredto, =oriby the thermal crackingorwis'flbreaking of. heavier petroleum. stocks. High-sulfurdistillates,.containingfromiul to 2% ortmore by weight :of sulfurcomefrom the. fractionation. of crude petroleum.

wThc. conditions in tthe .second L catalytic. zone are maindilferentfeed stocks to be subjected to hydrogenation are introduced. The numberof reactors andthenumber of catalyst beds in each 'reactor dependsbothupon the numberof feed stocks -to be'treated and upon the-exothermicheatof reaction that is releasabletor may be released in each catalystsection.

Accordingly, a primary objechof this invention is to provide a processfor simultaneously hydrogenating a number of feed stocks, differinggreatly in character from each. other.

Another object of this invention is to provide an integrated processionsimultaneouslyhydrogenating ,anumher of feedstocksrunder.optimunnconditions for each teed. stock wherein theexothermic. heat or. one reaction is .controlled by the.therrnaltcondition .oflthe' .hydrocarbon feed to the reaction zone.

A'ihild objectof theinvention is to proyide-aprocess wherein the-feedsareintrodueed separately into different reactionmzones sothat each maybe subjected to optimum process conditionsof temperature; time ercontact and, to some degree, I pressure and hydrogen-to-hydroearbonratio.

A fourth objecttof theinvention is ato provide a process forsimultaneously hydrogenating difierent- :feed stocks in a=plurality ofreaction zones using difierent catalysts in each zonetfor optimum 1oonversion of each er the feeds.

.Still another object:of the inventionds to providea 1 process v whereinthe feeds :are processed with various "catalysts under I differingconditions to produce separate and a totally difierent endfiproductsJThe only limitation :that may beplacedon the number.of reaction zones,and on the :feeds that may-hetreated, is-th'e ability of-the finalseparating system to recover the-various end-prod- Metswfor: furtheruse. It is. "obvious.th'at ifvthezproducts fromw-any two feedsarenotureadily: separated bytcommercial means, the feeds cannot:beadvantageously,treated ofreactiom products 'or: undesirable;byproducts; between reaction zones, 1 or recycling .rzof :hydrocarbons,unor are iSLlCh stepsrrequired in then successful applichtionrof ithestepswofitheinvention. i

Itais 5 tained such that .the second feed stock is desulfurized,

and any unsaturated aliphatic. compounds .are .saturated. Again, ssome.aromatic Jcompounds may -.also be partially hydrogenated, if: desired..At.the.samettime, the more refractoryufirst feed-.stock continues to behydrogenated, and also .actsras. a heat, carrier .to minimize :the.temperaturej increase due to.the exothermicheatof .the hydrogenationreactions.

A;third stream, whichmay, comprisetafeed stock which zjs lessrefnactorythan-the first 'twofeed. stocks, such as @a heavvstraight-rum.highrsulfur naphtha tor .a cracked naphtha, is introduced into a,third. catalytic zone along .Withathermdm sdrom thefir ttwo c aly izone Th tstr gh wmn. nap thazftac iom ut lize .asthe hird. fee may bebtainedw or cth .tr t n i n oft-crud P leum. A .crackedmaphtha for thispurpose is obtainable by thermal treatmentofi heayier petroleumtstocks,such aswo s ngwc s ua fu ls.- t ma v-c ia g5 dist la cr sis-breaking.The purpose of the, third zone is ,to desulfu le. and sa r t tuns til tsr lipha hydrocarb while the previous; feeds undergo .stillfurther-reaction. Eollowingthis, all of the pro ducts,-are;. conveyed afourth catalytic zone; tomeetand-mix with a fourth feed i h may mpr e alight, a un asolinwr l g cracked'naphthas boilingdnthe range of about to.3,0O,F. This fourth feed, which requires only y ery mild hr rgg i mixesw t t hs ici tr qdustsst from the ,fir st three reactors, within thefourth catalytic reaction zone. .Within the fourth reaction zone, .thele refractory feed is subjected todesulfurization, sweetening, andsaturation of olefins and diolefins for the purpose of producing, sweet,low-sulfur, light naphthas with good. color, odor and storage stability.t

FL -he. brief descriptionabove illustrates, the .use t of four reactionzones, but a greater or lesser-number of reaction zones are contemplatedas constituting this invention "The number of zones to be employed willbe dictatedby the number of feeds tohetrea ted, their,relativereactivity, and the, purpose for which the. products areintended. It follows, then, that the groupings of feed stocks andrelative introduction order in; the zones listed above are also subjectto change, again depending upon the individual characteristics of eachfeed and on the type .of product desired.

:Thesinvention is best: described in relation to the attached drawingwhich is a flow diagram of one embodiment of the invention using fourdifferent feed stocks. As shown in the drawing, the first feed ischarged to the system through line 2. Make-up hydrogen is conveyed byline 4 and joins recycle hydrogen conducted through line 6 to mix withthe first feed in line 2 wherein it is conveyed to heating tube 8 withinfurnace 10. The heated mixture of hydrogen and the first feed stockpasses through line 12 into the top of reactor 14. In the top of reactor14 is located first reaction zone 16. A second feed enters the systemthrough line 18 and mixes with recycle hydrogen from line 20 to passthrough coil 22 of furnace 10 and through line 24 into distributor 26located within reactor 14. The mixture of products from zone 16 and thesecond feed pass through zone 28 of reactor 14. The entire effluentproducts from zones 16 and 18 pass through line 30 and pressure-controlvalve 32 into second reactor 34.

The third feed enters the system through line 36, mixing with recyclehydrogen from line 38, passes through coil 40. of furnace 42, and thencevia line 44 to mix with the products in line 30 to enter the top ofreactor 34. Zone 46 of reactor 34 is operated under conditions optimumfor the third feed material, and the products therefrom pass downwardlyin reactor 34.

I The fourth feed enters the system through line 48, mixing with recyclehydrogen from line 50, passes through coil 52 of furnace 42, and thencevia lines 54 and 56 into distributor 58 located below zone 46 in reactor34. The mixture of the reaction products and the fourth feed pass intozone 60 of reactor 34. Alternatively, for further control of thereaction, portions of the fourth feed may be sent through line 62 intodistributor 64 before entering zone 66 within reactor 34. When heatcontrol is critical, any one or more of the feeds can be similarlyseparated between several of the catalyst beds as illustrated by passageof a portion of the fourth feed through lines 56 and 62. All of thereaction products leave the reactor through line 68, are cooled in heatexchanger 70, and passed into separator 72. Within separator 72, recyclehydrogen is taken off by line 74 and is recirculated by compressor 78into lines 6, 20, 38 and 50. Pressure controller 76 serves to maintainthe proper reaction pressure in reactor 34. The liquid products fromseparator 72 pass through line 80 and heat exchanger 82 intofractionator 84. Heat exchanger 82 may be employed to heat the productsto the proper temperature for fractionation.

In fractionator 84 the various modified products are separated intoseveral streams. The overhead stream passes through line 86 andcondenser 88 into separator 90. Any residual gas separated passes off inline 92 for use as fuel, or to a gas recovery system. The liquid productfrom separator 90 passes through line 94 and is divided into two parts.One part is returned by line 96 as reflux to fractionator 84, and theother is passed either to a stabilizer, gasoline storage, a fractionatorfor preparing feed for catalytic reforming, or a naphtha unit by line98. The use to which the overhead product is put will depend upon thefeeds employed in the process, the reaction conditions and the productsdesired. A side-stream of lighter material for eventual use as kerosine,diesel oil, or furnace oil is removed at line 100 and passes throughstripper 102 where it is stripped with steam entering at line 104. Theoverhead vapors from stripper 102 return to fractionator 84 by line 106.Stripped product is withdrawn through line 108. A reboiler systemconsisting of line 110, reboiler 112 and return line 114 is provided.Additional side streams may be removed from the fractionator, ifdesired. Reboiler 112 supplying heat to fractionator 84, may be heatedby steam, a reactor efiiuent, or any other suitable fluids passingthrough line 118. The hottoms product, or third product, consisting ofthe heavier material comprising gas-oil suitable for furnace oils orcatalytic cracking charge stock, is withdrawn, as another product fromthe system, through line 120 and passed through cooler 122 into line124.

It is apparent from this description of the process that the feedentering through line 2 passes over both catalyst bed 16 and catalystbed 28, and therefore, is subjected to reaction conditions for a longerperiod of time than the feed entering the system through line 18.Furthermore, one aspect of the invention comprises controlling thetemperature in catalyst beds 16 and 28 by controlling the temperature ofthe feeds in lines 12 and 24, independent of each other but within thelimits imposed by the heats ofreaction and the relative quantities ineach stream.

Further control of the reaction conditions is achieved by operating thereaction zones subsequent to reaction zone 28 at reduced pressure. Thisis accomplished by the use of pressure-control valves 32 and 76 in lines30 and 74, respectively. Control of the temperatures in each of thecatalyst beds by controlling the temperature of the operation of theheating coils 8, 22, 40 and ,52 is of particular importance. The time ofcontact of each feed in the respective zones is controlled by changingthe point of entry of the feed into the reactor. It is apparent fromthis description of the invention that when treating high- 1y refractorystock as the first feed, a higher hydrogen partial pressure would berequired. Thus, all of the hydrogen required for the feed entering atline 2 would be supplied by recycle hydrogen through line 6 plus anymake-up hydrogen added by line 4. As the reaction proceeds and some ofthe hydrogen is consumed and more feeds are being added to the system, alower hydrogen partial pressure will prevail in the subsequent catalystbeds 28, 46, 60 and 66. Consequently, the hydrogen partial pressure orthe hydrogen-oil ratio is increased by admitting more recycle hydrogenthrough lines 20, 38 and 50.

The catalyist used in each of the reaction zones may be any knownhydrogenation catalyst, such as the oxides or sulfides of cobalt,nickel, molybdenum, or tungsten, either singly or combined in varyingproportions, either unsupported or supported on a suitable carrier suchas clay, alumina, various alumina-silica combinations, or kieselguhr.

Examples of suitable catalysists that may be used are:

3% CoO+9-10% M00 on a support of Al O +5% SiO,,

3% CoO +12% M00 on an alumina support 10-20% MoS on an alumina supportEqual weights of WO -H O and NiCO converted to the sulfides to give a WSNiS catalyst.

Different catalysts may be used in the various reaction zones of thesystem. Since the first reactor or reaction zone 16 is subjected to moresevere duty, it may be constructed in duplicate so that one reactionzone can be regenerated while the other is on stream. The succeedingreaction zones 28, 46, 60 and 66 do not usually require frequentcatalyst regeneration and may be regenerated at the time of regularlyscheduled shut-down.

Any one or more of the plurality of feed hydrocarbons used may beintroduced as mixtures to constitute a first feed, second feed, etc., aslong as the first feed or first mixed feed is the most refractory stock,the second feed or mixture is less refractory than the first feed ormixture and so on. The third feed stock or mixture will be lessrefractory than the first or second feeds and the fourth feed or mixturewill be the least refractory. Since each feed may constitute a mixtureof hydrocarbons from different sources but having comparable refractoryproperties, the invention is not limited to processing four feeds orusing only four reaction zones as described in the drawing. In oneembodiment of the invention each feed may constitute a hydrocarbon froma single source and as many as four to seven different reaction zonesmay be utilized. In another embodiment wherein the indicidual feeds mayeach comprise a mixture of two or more hydrocarbons of similarrefractory properties but from different sources,

I gar'greatennu'mher of lfQBdSllIlfi-Yubfl processed *using a fewerlnnumberaofireaction zones. EIn other .words, the nur nber ofsfeedsluscddoestnot 113116210 correspond tosthe number ofireactionrzones used andr thesqinventiomcan be :practiced by using bothmixtures andrsinglessource;ihydrocarhonsrfor one 011211101'69015thefeeds introduced. isimilarly; the num- -;ber;of;products: separatedadoes-.110t have to correspond to themumbenof feedsnintroduced'intouthesystem.

To:illustrate;.thecifollowing TablewI: shows how seven:llDW-qualitymstocks of progressivewrefractory .iproperties t 7arecreated by the process tofgthis invention,giving theconaditicmszuseduin;four:zonesrtomnoduee three separate products; anaphtha, a distillate fuel; and a catalytic cracking feed; stock.

10 :to :produce :three or; more superiorustocks:foradirect use 7 or forfurther processing to manufacture high-quality motor. fuels. 0 v .0 {Thecobalt'molybdatecatalyst-employed inrthezmxample Table I .QatalyticZone1 1 2 3 7 4 r i Tungsten-i- Oatalyst V Cobalt Molybdate Nickel SulfideReaction Conditions: i r ;,Anerage1emPq9F 0:800 1800 7 700 7700 AveragePress. p 600 590 500 .7 490 IN-HSV 3 6 6 3 Hydrogen; c.1f./bbl.: 0

Fresh Make-Up 1, 700 Fresh Recy01e 1,300 1-,567 278 7282 From previouszone.- i L 933 1, 622 1, 518 Total to zone 2, 500 1, 900 1,800Consumeduh 100 100 .7100

i i Heavy Ooker Light Virgin Heavy :mvirging 1 @Light Feed-1 a Cat. 7 jjGas Cat. Gas Goker, Nephtha. Ooker Cycle Oil Cycle Oil Naphtha. Naphtha-Oi1 Oil .SnXiun-WtUPercent 0.5 r 0.8 BrorninezNouuan i l 10 0 50,Oarbon Res. 10 0.3 0. 4 DistillationKASTM): 01B 550 i 410 650 560 720700 600 500 l, 500

Products Naphtha Distillate Fuel Catalytic Cracking Stocks FeedstockSulfur, Wt. Percent. 0.012 0.09 I 0.1 r

i =1 wIn; Table 1-,. 1) =LVHSV=Liquid :volume hourly space elocity,liquidrvolumes. of oil/:hn; per vol. of catalyst.

:JIIJ: theaabove examplepthe-:heavy catalytic cycle-oil andheavierlportion:of thc coker distillate are treated-to produce-asuperior.xcatalyticcracking feedstock having a lowisulfur content,improvedcarbon/hydrogen ratio, and :improved carbon residuenumberfindicative of coke formation upon: cracking). The'light catalyticcycle-oil feed, light: cokeradistillate, and:l-high-sulfurwirgin gas-oilare fides, .WS and NiS.

7 The temperature and pressure-conditions within reach of thereactionzonesaresubject to variationfrom-.theconditions cited in-TableI. ,The general limits of conditions including the hydrogen ratiosmaybe-stated for. the individual feeds and mixtures somewhat as-iollows:i

0. 0 Table II 1 Conditions No 7 7 Feed Description Zone HE, C. F./

No. wbbl.

i 0.5-2 700-850 soc-1,7000 12000-0000 1 I 0.5-2 700-850 sou-1,000moo-4.500 2 1-2.5 700-850 x500-1,:000 two-3,000 2 1-2.5 650-800son-1,000 ,1,500,-2,500 s 1. 5-3 050-800 "400-800 1',400-2,'400 a 1. 5-3000-750 400-700 1,400-2;400 4 2-4 600-750 300-700 1, 300-2, 300

Liouidmolumes oticharge per hour peryolumdot reactor-orhcatalyst,

From Table II it is seen that some overlap of temperatures betweensuccessive zones is possible. The pressures and rates of introduction ofhydrogen necessarily overlap to give the proper amount of leeway so thatgradations of conditions from zone to zone can be established which arebest suited for the individual feeds and to direct the formation of thedesired properties in the final products. The ranges given for liquidhourly volume space velocity (LVHSV) shown in Table II refer to the feedspecified and all catalyst zones which that.

feed contacts. In Table I the LVHSV values given applied to each zoneonly. Thus, the feed to the first zone contacts four sets of catalyst,the LVHSV in each zone is 3, 6, 6 and 3 respectively, for an overallLVHSV of 1. The conditions set forth in Table II apply also wheremixtures of the feeds are used. Thus, zone 1 is operated at 700850 F.,and 500-1000 p. s. i. at 2005000 C. F. of hydrogen/bbl. of feedComprising a mixture of feed 1 plus feed 2 in any proportions. Thereactions proposed in Table II may be carried out using seven differentsuccessive zones, each under the conditions set forth opposite theindividual feeds.

From this description it is seen that the invention has a number offeatures and advantages. By the process a number of feeds differinggreatly in character and having a range of refractory properties can betreated simultaneously to produce separate and totally differentendproducts. The feed hydrocarbons are introduced sepately or asmixtures having similar refractory properties, into different reactionzones so that each feed is subjected to process conditions which areoptimum as far as temperature, time of contact, and to some degree thepressure and hydrogen-to-hydrocarbon ratio. The passage of reactants isfrom one zone to the other, dispensing with the necessity of removal ofreaction products or undesirable by-products between reaction zones.Different catalysts can be employed in the various zones for optimumreaction for each feed introduced.

The invention comprises, therefore, broadly the steps of subjecting arefractory stock, or mixture of refractory stocks, to hydrogenation in afirst zone under conditions to desulfurize the feed, saturate anyolefinic material and transform any ring compounds present. The productsformed are passed to a second zone along with a second feed comprisingless refractory hydrocarbons or mixtures of such hydrocarbons fromdifferent sources. The second zone is operated under conditions designedprimarily to desulfurize and hydrogenate the second stock while at thesame time partially converting or finishing the first stock and takingadvantage of its heat capacity to main tain the reaction conditions inthe second zone. The combined reaction products are sent to a thirdreaction zone along with a third feed hydrocarbon which is still lessrefractory than the first two feeds or feed mixtures. This third feedmay comprise a mixture of selected stocks, and conditions within thisthird zone are adjusted to desulfurize, hydrogenate and transform thethird feed into more desirable stocks, taking advantage of the heatcapacity of the products from the first two zones and further completingtheir reaction and inter-action under milder conditions. The over-allcombined products from this third zone may be separated at this pointor, preferably, are sent to a fourth zone along with a fourth feedhydrocarbon or mixture which is even more non-refractory.

Conditions in the fourth zone are adjusted to obtain primarily thedesulfurization, hydrogenation and transformation, such as colorimprovement, of the fourth feed again using the heat of the reactionproducts and unreacted materials from the previous zones to aid thereaction, cause inter-actions and a general leveling of products so thatthe final overall products may be separated into improved materials. Thefinal products may comprise naphtha suitable for use as gasoline orgasoline blending stock, distillate fuel oils, and catalytic crackingfeed stocks of low sulfur content and low carbon residue.

By the term refractory as applied to the feed materials used herein ismeant resistance to hydrogenation and reactions associated withhydrogenation.

The amounts of each feedemployed may vary with the capacity of theindividual reaction zones and available process equipment or the amountsof desired products. .In those instances where greater proportions ofhighly refractory feeds are used as compared with the proportions ofless refractory naphtha, the yield of cracking feed stock will beincreased and the yield of naphtha, in proportion, will be less. Theprocess is particularly well suited for the conversion of heavy andlight catalytic cycle oils gas oils, and various naphthas into increasedyields of light naphtha, distillate fuel stocks, and catalytic crackingfeed stock having enhanced properties. Hydrogen for the process isavailable from cracking, dehydrogenation and reforming reactions towhich some of the end-products are advantageously subjected. Thus, partor all of the hydrogen for the process may come from the reforming ofthe naphtha produced or the cracking of the heavier products produced.

Although the invention has been illustrated by several examples, theyare in no way limitingand the only limitations attaching to theinvention appear in the appended claims.

What is claimed is:

1. The process of upgrading a plurality of hydrocarbon feed stocks fromdifferent sources in a plurality of directly connected reaction zonesmaintained under hydrogeneration conditions comprising introducing arefractory hydrocarbon stock into a first zone maintained at atemperature at least about 800, introducing a second hydrocarbon feedstock less refractory than the first feed stock into a second reactionzone maintained at a temperature of at least about 750 F., introducing athird hydrocarbon feed stock less refractory than said second feed stockinto a third reaction zone maintained at a temperature of at least about700 F., introducing a fourth hydrocarbon feed stock into a fourthreaction zone maintained at a temperature of at least about 650 F.,conveying the reaction products formed into each successive r reactionzone, maintaining an incremental decrease in temperature successively ineach zone from said first to said fourth zone and separating thecombined reaction products from the last zone into at least two productsof enhanced properties. i

2. The process in accordance with claim 1 in which the first feed stockis selected from the group of heavy catalytic cycle oil having a boilingrange of about 500 to 730 F., coker gas oil having a boiling range ofabout 400 to 710 F. and mixtures thereof, said first reaction zone ismaintained at a temperature of between about 700 to 850 F. withpressures between about 500 to 1000 pounds per square inch, said secondfeed stock is selected from the group consisting of light catalyticcycle oil having a boiling range of about 400 to 600 F., virgin gas oilhaving a boiling range of about 410 to 610 F. and mixtures thereof, saidsecond reaction zone is maintained at a temperature of about 700 to 850F. with pressures of about 500 to pounds per square inch, said thirdhydrocarbon feed is selected from the group of heavy coker naphthahaving a boiling range of about to 385 F. and mixtures thereof, saidthird reaction zone is maintained at a temperature of about 650 to 800F. with pressures of about 400 to 800 pounds per square inch and saidfourth reaction zone is maintained at a temperature of about 600 to 750F. at a pressure of about 600 to 750 pounds per square inch.

3. The process of upgrading hydrocarbons from different crude oilsources in a plurality of interconnected reaction zones maintained underhydrogenation conditions comprising subjecting a mixture of heavycatalytic cycle oil and coker gas oil to contact with hydrogen in afirst reaction zone at a temperature of about 800 F. and a pressure ofabout 600 pounds per square inch with about 2000 cubic feet of hydrogenper barrel of feed, passing the reaction effiuent from the first zonedirectly into a second reaction zone along with a mixture of lightcatalytic cycle oil and virgin gas oil at a temperature of about 800 F.and a pressure of about 590 pounds per square inch with about 2000 cubicfeet of hydrogen per barrel of feed, passing the reaction efiluent fromsaid second zone directly into a third reaction zone along with amixture of heavy coker naphtha and virgin naphtha at a temperature ofabout 700 F. and a pressure of about 500 pounds per square inch withabout 1900 cubic feet of hydrogen per barrel of feed, passing thereaction effluent from said third reaction zone directly into a fourthreaction zone along with a light coker naphtha at a temperature of about700 F. and a pressure of about 490 pounds per square inch with about1800 cubic feet 10 of hydrogen per barrel of feed, the feed to saidfirst reaction zone being the most refractory and the subsequent feedsbeing successively less refractory, separating from the entire reactionefiluent a naphtha, a distillate fuel stock and a catalytic crackingstock, each characterized by their decreased sulfur content, decreased.unsaturation and decreased carbon residue.

4. The process in accordance with claim 3 in which the first threereaction zones contain a catalyst comprising cobalt molybdate.

5. The process in accordance with claim 3 in which the fourth reactionzone contains a catalyst comprising tungsten sulfide.

References Cited in the file of this patent UNITED STATES PATENTS2,587,987 Franklin Mar. 4, 1952 UNITED STATES PATENT OFFICE CERTIFICATEOF CORRECTION Patent No. 2,878,179 March 17, 1959 Harvey Hennig It ishereby certified that error appears in the-printed specification of theabove numbered patent requiring correction and that the said LettersPatent should read as corrected below.

Column 2, lines 5'and 11, for catalyatic", each occurrence, readcatalytic column 4, line 42,, for catalysists read catalysts line '73,for "indicidual' read individual columns 5 and 6, Table II,

fourth column thereof, in the heading, for "LVHSl read LVHSV column 8,lines Bl and 32 ,1 for "hydrogeneration" read. hydrogenation line 62,for lOOpounda" read 1000 pounds M.

Signed and sealed this 30th day of June 1959..

gsEAL) ttest:

KARL AXLINE I ROBERT C. WATSON Attesting Officer Commissioner of Patents

1. THE PROCESS OF UPGRADING A PLURALITY OF HYDROCARBON FEED STOCKS FROMDIFFERENT SOURCES IN A PLURALITY OF DIRECTLY CONNECTED REACTION ZONESMAINTAINED UNDER HYDROGENERATION CONDITIONS COMPRISING INTRODUCING AREFRACTORY HYDROCARBON STOCK INTO A FIRST ZONE MAINTAINED AT ATEMPERATURE AT LEAST ABOUT 800*, INTRODUCING A SECOND HYDROCARBON FEEDSTOCK LESS REFRACTORY THAN THE FIRST FEED STOCK INTO A SECOND REACTIONZONE MAINTAINED AT A TEMPPERATURE OF AT LEAST ABOUT 750*F., INTRODUCINGA THIRD HYDROCARBON FEED STOCK LESS REFRACTORY THAN SAID SECOND FEEDSTOCK INTO A THIRD REACTION ZONE MAINTAINED AT A TEMPERATURE OF LEASTABOUT 700*F., INTRODUCING A FOURTH HYDROCARBON FEED STOCK INTO A FOURTHREACTION ZONE MAINTAINED AT A TEMPERATURE OF AT LEAST ABOUT 650*F.,CONVEYING THE REACTION PRODUCTS FORMED INTO EACH SUCCESSIVE REACTIONZONE, MAINTAINING AN INCREMENTAL DECREASE IN TEMPERATURE SUCCESSIVELY INEACH ZONE FROM SAID FIRST TO SAID FOURTH ZONE AND SEPARATING THECOMBINED REACTION PRODUCTS FROM THE LAST ZONE INTO AT LEAST TWO PRODUCTSOF ENHANCED PROPERTIES.